macos: Mac program that limits the use of the Internet so that it is impossible to use at certain times

I'm wasting too much time online and I want my Mac to be unable to access the Internet during certain times of the day. I'm looking for something at the system level, not a browser add-on or parental controls. Also, I am not the owner of the router I am using, so nothing can be changed. I am looking for a software that, after granting all the privileges of administrator, it is IMPOSSIBLE to access the Internet without formatting my computer.